Fork lift truck



Jan. 8, 1963 H. BECKER 3,072,418

FORK LIFT TRUCK 4 Sheets-Sheet 1 F/GT la Jan. 8, 1963 H. BECKER3,072,418

FORK LIFT TRUCK Filed April 19, 1960 4 Sheets-$1 991; 2

Z2 M 5 h 56 M53 :iii' 7g 88 W" H1 H6. 4

I'" I 66 1* P 36 68 #4 4 8 ail $2 2 Arrylr,

H. BECKER 3,072,418

FORK LIFT TRUCK 4 Sheets-sheaf 3 Jan. 8, 1963 "Ill!" wan-J00 DMM m FIG.6 m4 :u 032w nu M V 71459115551154I!!! fill I Filed April 19, 1960 Jan.8, 1963 H. BECKER 3,072,418

FORK LIFT TRUCK Filed April 19, 1960 4 Sheets-Sheet 4' FIG. 7 ,//0

4; Z8 60 :g 42 1} 5a 40 INVENTOR: flA/VS fifc/(FR tow M m United StatesPatent Office The present invention relates to a fork lift truck, andparticularly to a hydraulic fork lift truck.

Hydraulic lift trucks now known generally consist of a front carriagewith steerable front wheels and a hydraulic lifting jack operation in avertical direction, and a rear carriage borne by a lift member or pistonof the hydraulic lifting jack. The rear carriage comprises a lift forkhaving two fork tines which are connected with each other via a pair oftransverse shafts. A lift arm is connected to one shaft. The lift armacts on the end of the lift fork facing the front carriage. On the endsof the tines extending rearwardly away from the front carria-ge thereare arranged vertically adjustable wheel suspensions. n the forward endof the fork at the crossbar the lift arm is vertically supported. A liftshaft is rotatably supported at the forward end of the fork and isjoined at one end to the front carriage by a connecting link or linksseated nonrotatably on the shaft. At its other end, the lift shaft actsvia a lever system on the vertically adjustable wheel suspensions. Whenthe lift jack is operated, the lift shaft is turned and a verticaldisplacement of the wheel suspensions is effected simultaneous with thelifting of the lift fork.

In the prior known lift fork trucks, the fork tines of the lift forkwere connected rigidly with each other by a transverse member. The liftarm was supported in or on this transverse member and the hydraulic liftmember was fastened to the lift arm. In order to impart to the lift forkthe required stiffness to resist twisting, the fork tines had to beconnected in a rigid nondetachable manner with the transverse member.This necessitated a considerable amount of labor and material.Furthermore, because of the rigid non-detachable connection of the forktines with the transverse member, a large number of lift forkscorresponding to the many diversified requirements of customers had tobe kept in stocks of dealers at all times. Also, the rigid one-piececonstruction of the lift forks took up considerable space in storage andtransportation.

The present invention is directed at overcoming the foregoingdifiiculties and disadvantages by providing a lift truck having a novellift fork construction. The lift fork includes a lift arm and fork tineswhich are separably interconnected. The tines and lift arm are connectedby spaced horizontal lift shafts. Each fork tine includes a beam ofchannel or box profile and having a channel or box superstructuresecured thereto. The superstructure may be detachably or integrallyjoined to the tine. The spaced lift shafts for the lift arm and tinesare seated in the superstructures of the tines. Due to the separableconstruction of the tines, superstructures, lift shafts and lift arm,the entire assembly can readily be disassembled for shipment and storagein the most economical and space saving arrangement. If any onecomponent is damaged in use, it can readily be replaced. Due to theseparable structure, fork tines of different sizes can be combined withdifferent sizes of connecting 3,072,418 Patented Jan. 8, 1963 The liftarm preferably has a box profile. The connecting lift shafts passtransversely through opposite sides of the hollow lift arm. The lift armis connected with the piston rod of the hydraulic jack by a universaljoint. Connecting links are fastened in a non-turnable manner on one ofthe lift shafts at opposite sides of the lift arm. These links arepivoted on pivot pins arranged parallel to the lift shafts and carriedby the front carriage of the lift truck. The pivot pins may be carriedon a cross-member which is turnable about a steering column of the frontcarriage and supported so that it is fixed against movement in the axialdirection of the steering column.

Within the superstructures of the lift tines there are disposed crankswhich act via a lever system on the wheel suspensions of the rearcarriage.

It is possible to provide a telescopic type of hydraulic jack forlifting the fork. Such a type of jack permits the amount of powerexpended in lifting the fork to remain substantially constant during thevertical movement or stroke of the fork.

It is therefore one object of the present invention to provide a lifttruck in which a lift fork includes separate and detachable tines havingsuperstructures connected by lift shafts, at least one of which shaftsis journaled for rotation in the superstructures. v

A further object is to provide a carriage for a lift truck in which afork includes separate and detachable tines having superstructuresconnected by spaced lifting shafts passing through a lift arm, one ofthe shafts being connected by a linkage to wheel suspensions fordepressing the wheels while the tines are lifted.

Another object is to provide a lift truck provided with a telescopichydraulic jack for lifting a lift fork.

Still another object is to provide a lift fork structure including tineshaving superstructures connected by lift shafts rotatably seated in thesuperstructures with ball joints for one of the shafts to permit limitedindependent movements of the tines.

Other and further objects and advantages of the invention will becomeapparent from the following descrip' tion taken together with thedrawing, wherein:

FIG. 1 is a side view of the lift truck in accordance with theinvention, partially in section, with the lift fork in lowered position;

FIG. la is a section along the line Ia-Ia of FIG. 1;

FIG. 2 is a side view, corresponding to FIG. 1, partially in section,with the lift fork in raised position;

FIG. 3 is a section along the line III-III of FIG. 1;

FIG. 4 is a section along the line IVIV of FIG. 2;

FIG. 5 is a section corresponding to that of FIG. 4 showing a modifiedembodiment;

FIG. 6 is a section through a front truck, equipped with telescopic liftjack, with the lift jack in retracted position; and

FIG. 7 is a section corresponding to that of FIG. 6 with the lift jackin extended position.

The lift truck shown in side view in FIGS. 1 and 2 consists of a frontcarriage 10 and a rear carriage 12. The front carriage 10 comprises apair of Wheels 14. The Wheels 14 are supported on an axle 16. This axle16 is a floating half-axle and is fastened to the lower end of asteering column 18 by a hinge pin 20. The steering column 18 is rigidlyfastened to the lower end of a housing 22. This housing 22 contains apump (not shown) which is actuated by a rocker lever 24 and a hydraulicjzazk (not shown). The hydraulic jack has a piston rod The piston rod 26is connected via a pin 28, the axis of which lies in the plane of thedrawing, with an articulation member 30. The articulation member 30bears at its upper end a fork 32 (see FIG. la.) The fork 32 is pivotedby a pivot pin 34 to a lever arm 36, which has a U-profile. The fork 32has some play in axial direction on the pivot pin 34.

A cross-member 38 is turnably supported on the steering column 18. Thiscross-member 38 is held fixed in axial direction of the steering column18 by a thrust plate 40. The cross-member 38 bears two pivot pins 42exetnding through bosses 43 formed on member 38.

The rear carriage 12 comprises a fork with two fork tines 44. The forktines 44 bear superstructures 46 on their ends facing the front carriage10. The superstructures 46 are welded firmly onto the forks 44. Thesuperstrutctures 46 are traversed by a lift shaft 48 and an aditionalconnecting lift shaft 50 (see FIG. 4). The horizontal, parallel liftshafts 48 and 50 are supported in each of the superstructures, the shaft48 in bearings 54 and the shaft 50 in bearings 52. The shaft 48 isturnably supported in the bearings 54. By means of the shafts 48 and 50,an approximately rigid connection of the two superstructures 46 and thusof the two fork tines 44 is produced. On the lift shaft 48 there areseated in non-turnable manner sleeves 56. These sleeves are welded orkeyed onto the shaft and bear connecting arms 58. The connecting arms 58are provided with connecting eyes 60 which extend around the pivot pins42 of the cross-member 38. The lift shaft 48 passes through the lift arm36 and is turnably supported with the sleeves 56 in bushings 62 of thelift arm 36. The shaft 50 also traverses the lift arm 36. It it providedwith sleeves 64 at the place of passage through the lift arm 36, thesesleeves being supported in non-turnable manner in bushings 66 of thelift arm.

The superstructures 46 are carried on the shafts 48 and 50.

Within the superstructures 46, cranks 68 are fastened to the lift shaft48, for instance by welding or keying. These chanks 68 can also befastened to the lift shaft 48 after the superstructures 46 have beenmounted in place. The cranks 68 are bored at their free ends. A pivotpin 70 is inserted in the bores. The pivot pin 70 passes through a pivoteye 72 at one end of an angle bar 74. The angle bar 74 bears at itsother end a pivot eye 76. This pivot eye 76 engages around a transversebar 78 of a bent strap 80. The bent strap 80 is rotatably supported on ashaft 82 by means of bearing eyes 84. The shaft 82 is supported in theprofile beams forming the fork tines 44. A wheel 88 is turnablysupported on another transverse bar 86 of the bent strap 80.

When the hydraulic lift press of the front track is moved out intoextended position, the lift fork is raised by the lift arm 36. Themovement of the lift fork upwards effects a rotation of the lift shaft48 (see FIGS. 1, 2). Due to this rotation, the angle bar 74v is pressedtowards the right by the cranks 68 and the bent strap 80 is turned inclockwise direction around the shaft 82. In this way, the wheels 88 areforced downward against the supporting surface on which the fork lifttruck rests.

A modified embodiment is shown in FIG. 5. The superstructures 46a taperin upward direction in. this embodiment. The connecting shaft 50a issupported by means of ball joints 90 in the superstructures. In the liftarm 36a, a bushing 92 is provided through which passes shaft 50a. Thisbushing 92 surrounds the shaft 50a with the interposition of an elasticsleeve 94. Because of this type of support of the shaft 50a, the liftfork has a certain flexibility, i.e. the two fork tines 44a can beturned independently somewhat around the lift shaft 48a.

In FIG. 6 there is shown a section through a front truck which,differing from the embodiment of FIG. 1, is equipped with a telescopiclift jack. The housing 22a comprises a tank or container 96 of fluid. Atthe bottom of the container is a cylinder 98. In the cylinder 98 isprovided a guide ring 100. In this guide ring 100 an annular piston 102is guided. Annular piston 102 is also is also guided by a guide bushing104 in a cover 106 of the tank 96. A nipple 115 on the cover opens intotank 96. Within the annular piston 102 another piston 108 is guided.This other piston has a piston rod 110. Piston rod 110 is guided in ajournal bearing 112 of ring piston 102 and at its free end bears a ball114 of a universal joint. To the annular piston 102, there is fastened astop ring 116 which limits the movement of the annular piston downwardby interaction with the guide ring and limits the movement of theannular piston upward by interaction with flange 103 of guide bushing104.

If liquid L is introduced into the cylinder 102 by application ofhydraulic pressure via nipple 115, a joint displacement of the twopistons 102 and 108 first of all takes place. Only after the ring 116comes against the bushing 104 is the piston 108 displaced with respectto the annular piston 102. The telescopic lift press is shown inpartially extended position in FIG. 7.

Various changes and modifications may be made without departing from thespirit and scope of the present invention and it is intended that suchobvious changes and modifications be embraced by the annexed claims.

What is claimed is:

l. A fork lift truck comprising front and rear carriages, said frontcarriage including a horizontal sup port, steerable wheels carrying saidsupport, a hydraulic jack on said support, said jack having verticalmovable piston means, said rear carriage including a pair ofhorizontally spaced fork tines, a horizontal lift shaft rotatablymounted on said tines, link means connected at one end to said liftshaft and connected at the other end to said support, another horizontalshaft parallel to the horizontal lift shaft and engaged with said tines,a vertical lift arm connected at one end to said other horizontal shaftand connected at its other end to said piston means, other wheels forsupporting said tines, and means operatively connecting said otherwheels to said horizontal lift shaft for adjustably spacing said otherwheels vertically from said tines as the tines are elevated by said liftarm, the horizontal shafts being the sole connection means between thetwo tines.

2. A fork lift truck according to claim 1, wherein said other horizontalshaft is twistable with respect to the horizontal lift shaft so that thewheels remain in contact with an uneven floor in all positions of thetines when under load.

3. A fork lift truck according to claim 1, wherein each of said tineshas two spaced upright walls, at least one of the shafts being connectedtwice to each tine at the upright walls thereof.

4. A fork lift truck according to claim 1, further comprising elasticmeans connecting said other horizontal shaft to said vertical lift armand to said tines.

5. A fork lift truck according to claim 1, further comprising pivotmeans connecting said other horizontal shaft to said vertical lift armand to said tines.

6. A fork lift truck according to claim 1, wherein the means connectingsaid other wheels to the horizontal lift shaft includes a pair of bentstraps, each of the straps rotatably carrying a different one of theother wheels at one end thereof. means pivotally mounting each strap toone of the tines, a crank in each tine connected to the horizontal liftshaft, and a bar in each tine connecting each crank to the other end ofthe strap thereat.

References Cited in the file of this patent UNITED STATES PATENTS2,274,164 Quayle Feb. 24, 1942 2,925,999 Hopkins Feb. 23, 1960 FOREIGNPATENTS 1,173,431 France Oct. 27, 1958

1. A FORK LIFT TRUCK COMPRISING FRONT AND REAR CARRIAGES, SAID FRONTCARRIAGE INCLUDING A HORIZONTAL SUPPORT, STEERABLE WHEELS CARRING SAIDSUPPORT, A HYDRAULIC JACK ON SAID SUPPORT, SAID JACK HAVING VERTICALMOVABLE PISTON MEANS, SAID REAR CARRIAGE INCLUDING A PAIR OFHORIZONTALLY SPACED FORK TINES, A HORIZONTAL LIFT SHAFT ROTATABLYMOUNTED ON SAID TINES, LINK MEANS CONNECTED AT ONE END TO SAID LIFTSHAFT AND CONNECTED AT THE OTHER END TO SAID SUPPORT, ANOTHER HORIZONTALSHAFT PARALLEL TO THE HORIZONTAL LIFT SHAFT AND ENGAGED WITH SAID TINES,A VERTICAL